alt Hacker Newsone thing I always forget about, is that you have a whole network of 127.0.0.0/8 , not just one IP.
So you can create multiple addresses with multiple separate "domains" mapped statically in /etc/hosts, and allow multiple apps to listen on "the same" port without conflicts.
I never thought of using localhost like that, I'm surprised that works actually. Typically, if you want a private /8 you would use 10.0.0.0/8 but the standard 192.168.0.0/16 gives you a lot of address space ( 255^2 - 2 IPs (iirc) ) too.
..actually this is very weird. Are you saying you can bind to 127.0.0.2:80 without adding a virtual IP to the NIC? So the concept of "localhost" is really an entire class A network? That sounds like a network stack bug to me heh.
edit: yeah my route table on osx confirms it. very strange (at least to me)